*Loaded cars with empty-load brakes are to be considered the equivalent of one and one-half (1½) cars in determining tons per operative brake.[1]

Tonnage of operating locomotive(s) not in dynamic braking is not to be used in determining tons per operative brake.

The instructions in Timetable No. 2 indicate that the descending grade between Hiland and West Colton is covered by rule 33. The timetable also lists the maximum tons per operative brake for trains descending the grade and the exceptions for those trains using dynamic braking (appendix H). The instructions also state:

Insufficient dynamic brake capacity or failure of dynamic brake which results in exceeding these tonnages per axle, is to be considered as operating without dynamic brake.

Should dynamic brake failure occur on one or more locomotives resulting in insufficient dynamic brake capacity, train must stop and all retaining valves turned up. Train may then proceed not exceeding 15 mph if, in the judgement of the conductor and engineer, it is safe to do so.

The SP’s general road foreman of engines provided the Safety Board with a speed decision flow chart for Rule 33 (see figure 15). According to his testimony, "A train consisting of 69 cars with a weight of 8,900 tons and that had 18 operative dynamic brake axles" would not have been allowed to descend the grade east of Hiland. Extra 7551 East on the day of the accident had 128 tons per operative brake (8,900 trailing tons divided by 69 (number of cars in train, not using the 1½ braking equivalence)) and 494 tons per axle of dynamic braking (8,900 trailing tons divided by 18 (three locomotive units with six axles each)). Using the speed decision flow chart, the general foreman illustrated why the train was not permitted to operate (follow arrow #1 on figure 15). Using the chart, the general foreman also illustrated the decision process the engineer would have made on the day of the derailment with the information that he had 69 tons per operative brake[2] (follow arrow #2 on figure 15). According to the general road foreman, "If the train would have 6,151 tons, with the information that [the head-end

↑SP cancelled this rule by special instructions, effective May 22, 1989.